MH wont start on chassis battery. Has 13V

darsben1 wrote:
Is the chassis battery disconnect switch off?

The "stock" disconnect switch (on most units) is for the house, not the truck chassis.

(Edited correction)

Wondering if you connected all cables when you replaced the batteries?

BIG HINT: Always mark all cables and take pictures before you start. A club members friend replaced his batteries and the rig would not start. He was in total denial that they weren't connected correctly. After he finally calmed down and let me look I found a unconnected cable.

The combiner or boost is a solenoid that connects the 2 battery banks. It should be reasonably close to both battery banks.

OP Your unloaded voltage readings don't mean much. Connect your voltmeter to a good FRAME ground. Then when trying to start measure to the negative battery post (should be almost 0V) then the positive battery post (should be 12V+). Continue towards the starter until you find the problem.

New batteries fail - have them load tested.

Is the chassis battery disconnect switch off?

wa8yxm wrote:

There is a hint here Try cleaning connections.

And the second hint is:
Test the chassis battery under load.
The no-load voltage reading is often meaningless.

Happened to me 4 times
1st time I disconnected and re-connected the battery (Cleaning the connection)
2nd Time.. Same as the first, 3rd, Likewise

4th time the batteries failed load testing.... (well design life is 7-10 years and they were 9 years old so no complaints)

There is a hint here Try cleaning connections.

MrWizard wrote:
Loose dirty corroded connections between chassis battery and combiner
When you hit boost you get the good clean solid connections from the house battery
Key, ignition starter, cables are probably OK

Hi, this sounds like the best theory.. because the starter connections must be ok if it works with boost.

My batteries were all dead in storage.. i replaced the two chassis because i know when they got to 1V they were goners. The deep cycles were only 1 year old and seemed to come back alive ok.
So chassis battery are brand new.. but i did personally connect them... so i will remove the battery connections this morning and put some sandpaper to them and see if that helps.

Where is the combiner or what does it look like? I know every coach is different but any help on finding it is appreciated. Do chassis battery go to this combiner first and then to the "chassis"?

One question-- if i turn the key and check battery voltage, there should be some drop, right? I am going to test that this morning too. If they fall to 11.5V then I guess the batteries are toast. But if they dont even budge.. is that really just a bad battery connection? I ask because the voltmeter on the dash doesnt budge.. so i think it is not even trying to draw power

Loose dirty corroded connections between chassis battery and combiner
When you hit boost you get the good clean solid connections from the house battery
Key, ignition starter, cables are probably OK

Did you clean and tighten the battery terminals?

How old is your battery. You can have a battery that will show your voltage with a surface charge after disconnecting charge circuit, but does not have cranking amps necessary.

doublev wrote:
I have a 2008 Country Coach Affinity. It will not start (not even try to crank) on the chassis battery. Everything lights up on the dash OK, it even shows 13V on the voltmeter. Turn the key and nothing.

If I hit the battery boost (which combines chassis with house battery) then I can start it fine.

I confirmed the batteries have 13V by disconnecting from shore power and putting voltmeter to the chassis battery. 13.05V. I checked the coach batteries (at this point they were running on the inverter) and they came in at 12.5V.

I think I can rule out the batteries... but I dont understand what is so special about battery boost-- why would the engine start on that if it is not the battery?

this is an automotive problem.

how long had the chaddis battery been isolated before you took the reading? you need to wait 5-10 mins before taking the reading.

also, check to see you have 12-volts at the solonoid switch and starter. sounds like a bad/loose connection and the boost is getting enough voltage to spin the starter. i'm betting on the starter connection.